The present invention relates to a conductive lead for miniature capacitors and a process for joining such conductive leads onto miniature capacitors. More particularly, the present invention is related to a conductive lead suitable for use with an automated process for positioning conductive leads relative to the terminals of a miniature ceramic capacitor and for fixing the leads to the terminals.
Present technology for joining conductive leads onto miniature capacitors, i.e., capacitors wherein the major dimension is on the order of less than about 0.300 inch, has not kept pace with the increased demand for such capacitors. Aside from joining the lead wires by hand, which is a painstaking procedure considering the relative dimensions of the articles involved, the most common procedure is to attach a row of U-shaped lead wires to a carrier, such as a piece of cardboard, cross one leg of each U over the other to create a spring-like tension between the opposed legs, insert the capacitor between the legs, and then solder the lead to the capacitor. The major disadvantage to this method is that, prior to soldering, each of the lead wires grasps the capacitor at an acute angle along opposing bottom edges of the capacitor, and thus the same spring-like tension which holds the capacitor between the legs also has an upward vector which acts on the edges to squeeze the capacitor out of such grasp. As such, while many capacitors will be held in place until the lead wires can be permanently connected, an unacceptable number of capacitors slip from the grasp of the lead wires and must be reinserted. Equally as deleterious, the juncture of the capacitor and each of the lead wires is point-to-point along the bottom edge of the capacitor, which is the smallest dimension of the capacitor. Thus, even after the capacitor is soldered to the lead wire the mechanical integrity of this point-to-point juncture is somewhat tenuous, notwithstanding the surrounding body of solder, and prone to failure.
Another common procedure is to form each of the lead wires with a step or platform intermediate the ends of the lead wire and to rest the capacitor on the platform against the lead wire. While this method overcomes the problem of the lead wires "ejecting" the capacitor and increases the surface contact between the lead wire and the capacitor, it requires the use of an external clamping device to hold the capacitor on the platform and against the lead wire when the capacitor is inverted, during subsequent processing, as for example, when it is dipped into a bath of solder, etc. The coordination of interaction between the clamping device, lead wires and capacitor can be difficult, given the size of the elements, and can result in misalignment and unacceptable components.
There thus exists a need in the art for a process which can quickly, efficiently, and effectively position a lead wire adjacent to the terminals of a miniature chip capacitor and can maintain the integrity of such a juxtaposition during the various steps which may be necessary to permanently join the lead wire and the capacitor.